Datasheet
SCEA017
7–286
GTLP in BTL Applications
A-Port/Daughter-Card Side of the Device
•
Logic levels – The logic levels are compatible because the threshold, V
IH
, V
OH
, and V
IL
logic
levels are the same. GTLP is 5-V tolerant.
• Transistor types and drive levels – They are not significantly different. Most applications do
not require the higher drive and work well with the balanced drive of ±24 mA. Also, GTLP is
offered with a series-damping-resistor (SDR) option that reduces the drive to ±12 mA, and
provides better signal integrity into smaller lumped loads.
• Bus hold – Neither device has the bus-hold feature. The A port of most GTLP devices that
do not feature the split 3-wire A port is featured with bus hold.
• Hot insertion – Both families support hot insertion with the I
off
and power-up 3-state (PU3S)
features.
B-Port/Backplane Side of the Device
•
Signal levels – Signal levels are not compatible (see Figure 4). The level of noise margin is
about the same; only the input thresholds of operation are different. As discussed in the
following paragraphs, GTLP devices can operate at BTL signal levels by changing V
REF
to
1.55 V and raising V
TT
to 2.1 V.
V
REF
= 1.0 V
V
OH
= 1.5 V
V
OL
= 0.55 V
V
TH
Lower noise margin
– 400 mV
0.00 V
0.25 V
0.50 V
0.75 V
1.00 V
1.25 V
1.50 V
1.75 V
2.00 V
V
IH
= 1.05 V
V
IL
= 0.95 V
V
REF
= 1.55 V
V
OH
= 2.10 V
V
OL
= 1.10 V
Lower noise margin
– 375 mV
V
IH
= 1.625 V
V
IL
= 1.475 V
GTLPBTL
Upper
noise
margin
Lower
noise
margin
Upper noise margin
– 450 mV
Upper noise margin
– 475 mV
Figure 4. BTL and GTLP Signal-Level Comparison